Liquid level indicating device



2 Sheets-Sheetv l H. B. BREEDLOVE LIQUID LEVEL INDICATING DEVICE Aug. 4, 1953 Filed May 17, 1951 m WQ m n T H E n w n 4 fw 4 .d e e ndumzunnzou @w 7 @I PQDWO( um 1a f W M1 ,rn a Q w H dOPljO MN@ @l mw dor J-30ud IWINMJJ uwJCUQ/.Qw duzncow lum-HZPUMG In Aug. 4, 1953 H. B. BREEDLOVE LIQUID LEVEL. INDICATING DEVICE 2 Sheets-Sheet 2 Filed May 17. 1951 l /l/ Il /l/ Patented ug. 4, 1953 LIQUID LEVEL INDICATIN G DEVICE Harry B. Breedlove, Baton Rouge, La., assignor to Standard Oil Development Company, a corporation of yDelaware Application May 17, 1951, Serial No. 226,805 3 claims. (c1. 340-199) This invention relates to liquid electrolyte level sensitive apparatus in general and more particularly relates to an apparatus of this type to indicate the presence or absence of foam or emulsion.

It is an object of this invention to provide a liquid electrolyte level indicator which is dependable, unaffected by non-conductive suspended matter in the electrolyte, relatively insensitive to changes in concentration of the electrolyte and without any corrodible or moving parts exposed to the liquid electrolyte.

In accordance with these and other objects, this invention provides a liquid level indicator comprising a signal generator feeding two inductance coils which are electrically connected to produce a magnetic field 180 out of phase, an interposed coil arranged to detect the degree of unbalance of the magnetic fields, an amplifier arranged to amplify any unbalance signal produced, and means to detect the difference in strength of the signal produced by the signal generator and the unbalance signal produced in the interposed pick-up coil.

An apparatus of this type is particularly suitable for detecting the height of foams or emulsion formed in the operation of many industrial processes and has particular application in the detection of foams and emulsion formed in artificial latices obtained as one step in the preparation of synthetic rubber by the emulsion technique.

The invention will be understood more readily in the detailed description thereof taken in connection with the accompanying drawing in which:

Fig. 1 is a diagrammatic representation of the general circuit layout of the present invention, and

Fig. 2 is a longitudinal cross-sectional view of the glass and metal well assembly containing the inductance coils.

Referring now to Figure 1, alternating current is supplied through leads l and 2 to a conventional rectier and voltage regulator 3 Oscillator 4 is a Wein bridge thermionic valve device operating at approximately '7000 cycles per second and is connected to rectifier and voltage regulator 3 by leads 5 and 6. The output from oscillator 4 feeds through discharge leads 1 and 8 and amplitude adjusting potentiometer 9 into inductance coils I and II connected so as to produce a magnetic field 180 out of phase. Interposed between coils I0 and II is coil I2 which is connected by conductors I3 and I4 to ampli- 2 fier I 5, the output of which is fed to bridge-type rectier I6 through isolation transformer I1. Electric power for the operation of amplifier I5 is supplied from rectifier and voltage regulator 3 through leads IB and I9. A signal from oscillator 4 also feeds a 'second bridge type rectifier 20 through conductor 2I, amplitude control potentiometer 22, and isolation transformer 23. The output from the two bridge rectiers is connected in series with relay 24 and milliammeter 25. The rectifiers I6 and 20 are connected in opposition so that the current flowing through relay 24 and meter 25 is the difference between the two currents flowing in the two rectifiers. Relay n 24 is of the normally closed type. The current from the oscillator is sufficient to hold it open. The contacts 26 of relay 24 are connected in series with alarm means 21 and a power source (not shown). If desired, additional relays may be added in relay 24 circuit where high current carrying capacity is necessary. Any failure in the equipment will cause contacts 26 of relay 24 to close, setting off the alarm.

'I'he operation of the device is as follows:

The oscillator or signal generator 4 is adjusted to the resonant frequency of the induct- -ance coils I0, I I and I2. The signal fed to the two outer coils I0 and II is adjusted in amplitude and phase to produce a minimum signal in coil I2. At the same time a signal from the oscillator 4 is fed to the bridge rectifier 20. Y The output signal from the amplifier I5 is fed to the second bridge rectifier I6 which is connected in opposition to rectifier 20. Any signal from coil I2 amplified in amplifier I5 will thus oppose the current from the oscillator 4 and cause relay 24 to close operating the alarm 21.

Referring now to Figure 2, reference character 3I designates the liquid input to a container 32. The container 32 contains liquid 33 at a variable level 34. A glass hollow member 35 depends from a metallic pipe 36 by means of adapter 31. The hollow member 35 is sealed at its lower end to exclude liquid and is partly irnmersed therein so that coil II is just above the liquid level. It supports therein the two outer inductance coils I0 and Il and interposed detector coil I2, each grounded to metal shield 38. Inductor leads 39 and 40 are connected to the two outer coils and lead 4I to the interposed coil. Metal shield 38 is connected to ground lead 42.

When the foam, emulsion or liquid dielectric level in the vessel is below coil II, the magnetic field around coils I0 and II is balanced and the signal picked up by coil I2 is at a minimum and the relay 24 is held open. Whenever the level rises around the inductance coils l and Il the strength of the magnetic elds around these coils is unbalanced and a signal is produced in coil I2. This signal is amplified and rectified and opposes the current in the relay circuit and closes relay 24 setting off the alarm 21.

The nature vof the present invention having been thus fully set forth and specic examples of the same given, what is claimed :as new and useful and desired to be secured by Letters Patentis:

1. Apparatus for detecting variation of level of liquids in a container vessel therefor, comprising a hollow casing member suspended within said vessel and sealed from communication therewith, a pair of nductance coil elements extended into said casing member disposed in spaced relation longitudinally of said casing, said elements each connected in an electric circuit to produce a magnetic eld about each'coil of substantially balanced strength substantially '180 out of phase, a third coil, interposed between said `pair -of coils within said magnetic elds, connected in a circuit adapted to transmit an induced current in said third coil upon vari-ation of the strength of one of saidmagnetic elds and means for registering said induced current.

2. An apparatus according to claim l in which said casing and the coils therein are vdisposed within said vessel with said coils above fthe nor- 4 mal upper level of the liquid contained in said vessel.

3. An lapparatus for sensing variation in the level of liquids in a container vessel therefor, comprising a pair of inductance coils, each connected in an electrical circuit adapted to produce substantially balanced magnetic fields out Aof phase, disposed in a surrounding media of substantially uniform reluctance within said vessel, a, third coil interposed between said pair of coils adapted to receive and transmit an induced current produced by unbalance of said magnetic elds upon variation of the media surrounding eitheror .both -said vpairs of inductance coils, and

means for registering said induced current connected'to said third coil.

HARRY B. BREEDLOVE.

References Cited in the le of this patent UNITED STATES PATENTS Number VName Date l2,136,219 Scherbatskoy Nov. 8, 1938 ,2,196,809 Headley Apr. 9, 1940 2,240,184 Hathaway Apr. 29, 1941 2,260,837 Kuehni Oct. 28, 1941 2,420,160 Adamson May 6, 1947 :OTHER REFERENCES Journal of Scientific Instruments. January 1948,pages 4-6. 

